Change Metaball stickyness
Play with the values for Threshold and resolution

From the Manual:
Threshold (Influence)

Threshold defines how much a meta’s surface “influences” other metas. It controls the field level at which the surface is computed. The setting is global to a group of Meta objects. As the threshold increases, the influence that each meta has on each other increases.
There are two types of influence: positive or negative. The type can be toggled on the Active Element panel while in Edit Mode, using the Negative button. You could think of positive as attraction and negative as repulsion of meshes. A negative meta will push away or repel the meshes of positive Meta objects.